Molded polyurethane foams are used extensively in various seating applications, including automobile seats. In order to provide comfortable seating, the current polyurethane foams must have breathability. The present method of attaining breathability involves the combination of mechanical and/or vacuum crushing with the appropriate silicone surfactants in the polyurethane foam formulation to provide maximum cell openness.
A typical solution to improving the air flow of molded foams is to select less stabilizing silicone surfactants for molded foam formulations. These less effective surfactants will provide more cell opening; i.e., better air flow values; however, more processing problems and overall rising foam instability are offsetting disadvantages. A second practice is to use a mixture of standard silicone surfactant with a dimethylsiloxane fluid. The dimethylsiloxane fluids are normally used as defoamers. These silicone blends work, but again, trade-offs in rising foam stability and processing latitude are necessary.
Catalyst compositions used in making polyurethane foam typically comprise a combination of a blowing catalyst and a gelling catalyst. The blowing catalyst influences the isocyanate-water reaction. Bis(dimethylaminoethyl)ether [BDMAEE] is a commonly used blowing catalyst. Polyurethane catalysts are not considered to have cell opening effects. At the levels used in industry to achieve optimum productivity, catalysts are typically blamed for decreasing cell openness by increasing the polymerization rate to polyurethane.
The polyol suppliers have worked at producing modifications of their products to improve cell opening. In addition, low levels of selected polyols are sold as cell opening modifiers. These polyols are typically low molecular weight polyols used in rigid foam applications.